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Servicing Square Taper Cranks

What you need

• Crank Puller Tool
• Socket Set
• BB Wrench
• Grease
• Copperslip
• Workshop Towl

Optional materials

• New Bottom Bracket Cartridge
• Torque Wrench
• Work Stand

This article will discuss the removal and installation of cranks from square spindle bottom brackets. Tools known as crank pullers are used for two basic crank types: the square spindle type arms, and the splined type spindle arms. If the bottom bracket cartridge is loose or seizing it needs to be replaced. Once removed the sizing is often written on the cartridge body if unknown.

An older Campagnolo Veloce 8 speed system will be used for an example but many other systems both old and new (including systems like Middleburn) still use this system of internal bottom brackets and tapered / splined cranks.

A traditional square tapered crank is shown above (collar on the left hand side - non-drive side).

A splined internal bottom bracket is shown above - the only difference in removing them is the bottom bracket tool needed, this is specific for each type of bottom bracket (Shimano, Campagnolo, ISIS).

Disassambly

Firstly remove any dust cap that may be present (some have a dust seal and crank bolt combined and feature a socket fitting) to expose the head of the crank bolt (some have a nut on a threaded spindle stud).

Using the appropriate socket (drive-side crank) hold the crank arm and turn counter-clockwise.

Removing the bolt usually exposes a washer - remove this washer and set aside.

Different crank pullers are available, some are incorporated in a wrench while others, like above, are stand-alone.

Firstly, after cleaning the threads in the crank recess, screw in the tool body, taking care not to cross thread it.

Tighten using a spanner up to around 5 nm - enough for the tool to stop rotating but not too much to strip threads.

Insert the tool driver (the hole in the axle on the newer hollow axle ISIS and splined bottom brackets require the modern crank extractors with the wider bore tip).

Screw in to take up the slack.

Using a spanner, holding the crank arm, rotate the spanner clockwise to push the driver in and push the crank off the axle.

When the crank arm comes off the tool will still be inserted (non-driveside crank pictured).

Remove the tool body anti-clockwise and then its free to use on the other crank.

Bottom Bracket Removal

When both cranks are removed they can be cleaned more easily. The play in the bottom bracket can be examined fairly easily.

Wrenches and tools are available to remove the bottom bracket.

Start first with the non-drive side as this is the collar side (not attached to the bottom bracket cartridge) and rotate anti-clockwise (sometimes, if stiff, use a rubber hammer to tap the end of the wrench). 

Rotate the wrench anti-clockwise on the drive side.

As you can see there is a cup and the bottom bracket cartridge.

Reassembly

The threads of the frame should be clean and if fitting to a new frame the faces clean and square with the frame - this is less of an issue compared with the alignment for external cup systems. I use copperslip but blue threadlock or grease will do (present corrosion and siezure).

I tend to use grease on the inner bearing cover to help seal it from mud and water ingress.

I also put a thin coating over the bottom bracket cartridge body to help reduce corrosion on cheaper cartridges.

The cartridge body should be screwed in by hand into the drive side (anti-clockwise) taking care not to cross thread it.

The cassette can then be tightened with a wrench  and if you have a suitable tool you can fit it to a torgue wrench (manufacturers often mark the cartridge body with the torque setting) - I feel that you should not tighten it using a hammer, just very tight by hand (70 nm as above). The non-drive side cup can then be fitted and tightened clockwise in a similar fashion.

Grease the axle tapers (stops creaking, corrosion and easier for removal).

Insert the cranks back on (180 degrees opposite each other of course).

Grease / copperslip the washers and nuts/bolts before refitting.

The cranks are pushed onto the axle by tightening the crank bolts (or nuts) - the torque setting varies so seek the manufacturers guidelines for this (approx 35 nm for Campag).

Put the dust caps back on and you're done.

Richard Fox - Features Contributor

Richard has been mountain biking for over 17 years,7 years on his local trails, Dartmoor. He also regularly rides away from home – usually riding each year (while doing the mechanics for others) in various events such as the Cheddar Challenge, Rough Ride, Soggy Bottom, Dyfi Enduro and twentyfour12.

All these years of riding (and breaking) bikes, has resulted in Richard acquiring the wealth of experience (and the tools) to keep his, and inevitably all his riding crew's, bikes on the trails. Richard is a Cyclist No.1 features contributor.

Maintenance in association with Cycle System Acadmey...

Cycle Systems Academy offers a range of courses, from one day introductory courses in Basic Maintenance, specialist courses such as Brompton Servicing, or learning how to strip out and repair Sturmey Archer Hubs, right through to professional industry training in Level Two and Level Three qualifications recognised and accredited by the Government Qualification and Credit Framework.

Cyclist No.1 has teamed up with Cycle Systems Academy to provide maintenance guides for the home mechanic.

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